Description / Abstract:

This part of IS0 5167 specifies the geometry and method of use (installation and operating conditions) of orifice plates, nozzles and Venturi tubes when they are inserted in a conduit running full to determine the flow-rate of the fluid flowing in the conduit. It also gives necessary information for calculating the flow-rate and its associated uncertainty.

It applies only to pressure differential devices in which the flow remains subsonic throughout the measuring section and is steady or varies only slowly with time and where the fluid can be considered as single-phase. In addition, each of these devices can only be used within specified limits of pipe size and Reynolds number. Thus this pari of IS0 5167 cannot be used for pipe sizes less than 50 mm or more than 1200 mm or for pipe Reynolds numbers below 4000.

It deals with devices for which direct calibration experiments have been made, sufficient in number, spread and quality to enable coherent systems of application to be based on their results and coefficients to be given with certain predictable limits of uncertainty.

The devices introduced into the pipe are called “primary devices”. The term primary device also includes the pressure tappings. All other instruments or devices required for the measurement are known as “secondary devices”. This part of IS0 5167 covers primary devices; secondary devices1) will be mentioned only occasionally.